This invention relates generally to cargo carriers such as trailers, intermodal containers, and the like employed in the transportation of goods. The invention particularly relates to cargo carriers made principally or wholly from aluminum alloy extrusions and plates.
In recent years, there has been growing interest in developing intermodal cargo containers suitable for transportation by truck, rail, or ship. With the dramatic increase in import and export trade experienced worldwide, the demand for such cargo containers has steadily increased. There has also been a steady demand that the intermodal containers, as well as trailers, be designed so as to have maximum volume capacity yet have outside dimensions within the laws and regulations applied to trailers and containers when they are being transported over the road by truck.
Many cargo carriers suitable for multi-mode transport of cargo have recognized standard dimensions, structural features that minimize handling problems, and allow for stacking of containers. However, there exist a number of different and changeable standards. For example, in recent years, due to the relaxation of the permitted width dimension allowed on over-the-road truck trailers, some attention has been directed to the construction of increased width containers to increase container capacity as disclosed in U.S. Pat. No. 4,844,672, and increased width trailers as disclosed in U.S. Pat. No. 4,904,017.
Another possible way for increasing cargo carrier capacity while retaining the outside maximum dimensions standardized by the industry regulations is by increasing the vertical height dimension of the interior of the cargo container. For example, the vertical height of conventional I-beam floor supports, as well as the thickness of wood flooring attached to the floor supports, can be reduced to increase the capacity of the cargo carrier. However, the structural requirements for supporting a defined load within cargo carriers does not permit substantial decrease in floor thickness using conventional materials or structures.
Inasmuch as cargo carriers, particularly intermodal containers, can on occasion be exposed to sea transport, it is important that any dissimilarity in metals be avoided in order to reduce any galvanic degradation of the cargo carrier. As is part of the desire to maximize the volume of such cargo carriers, there is also a desire to maximize the vertical inside height by providing a floor structure which is as thin as possible while time retaining the necessary strength required for the long duty life typically experienced by such cargo carriers.
These factors have led the inventors to focus attention on adopting a new floor structure, preferably made entirely of aluminum alloy, which would have sufficient strength and durability, and could be used on all types of cargo carriers including trailers and intermodal containers. A further object of the new floor structure is to provide a design which is suitable for use in cargo carriers employing a wide variety of structural elements taken from containers other than of aluminum alloy plate construction. Of particular interest was a desire to arrive at a construction which would permit easily repeatable assembly of cargo carriers even under close tolerance restrictions.
With the dramatic increase in import and export trade experienced worldwide, the demand has also steadily increased for cargo carriers, including both trailers and containers, having common features which would permit top handling of the cargo carrier by a common means. There has also been a steady demand that the cargo carriers be designed so as to have lift pockets which only minimally intrude into the interior volume of the cargo carriers.
These factors have led the inventors to focus attention on adopting a new lift pocket structure which would have sufficient strength and durability, and could be used on all types of cargo carriers including trailers and intermodal containers for simple engagement with pin, or pin and shoe, lift mechanisms. A further object of the new lift pocket structure is to provide a design which is suitable for use in cargo carriers employing a wide variety of structural elements taken from containers and trailers having other than aluminum alloy plate construction.
Accordingly, an object of the present invention is to provide a cargo carrier having substantially increased usable internal space through utilization of a novel floor structure having minimum vertical dimensions while retaining the necessary strength and providing the necessary lift pocket structure to permit stacking of the cargo carrier and contents in the conventional manner. Another object of the present invention is the use of such a novel floor structure together with a novel lift pocket structure in a cargo carrier having other volume maximizing features to achieve a very large cubic volume capacitor.